Method of protecting cut surfaces of pieces of wire



P. ZIEGS 2,247,829

METHOD OF PROTECTING CUT SURFACES 0F PIECES OF WIRE July 1, 1941.

Filed Feb. 1, 1939 Patented July I, 1941 METHOD or PROTECTING cU'r SURFACES or rmcss 0F WIRE Paul Ziegs, Pforzheim, Germany Application February 1, 1939, Serial No. 254,114 7 v In Germany December 10, 1937 4 Claims.

This invention relates to a method of protecting cut surfaces of pieces of wire, for example the cut surfaces of so-called dental pins, used to secure artificial teeth, which are made by cutting up wires or the like consisting of a core of base metal and a coating of noble metal and which are deformed, if desired, at the end or ends, for example by forming beads. by upsetting.

When such wires are cut up into pins, the base core metal is bared at the cut surfaces and thus exposed to corrosive influences, forexample to the influence of the juices of the mouth in the case of pins for artificial teeth. It is true that when the wire employed for the production of such pins is cut through the coating metal is generally drawn slightly over the end surface of the wire, but even when the coating'is thick it does not extend sufliciently far to cover the cut surface of the core metal completely. The

disadvantages of the exposed base core metal occur to an increased extent when the dental.

pins are provided at one or both ends in the usual manner with a broadened head, by upsetting, since the exposed cutsurface of. the base metal of the core is thereby also enlarged.

Various attempts have already been made to obviate this drawback. For example, it has been proposed to provide the entire pin'with a further electrolytic coating after the pin has been given its final shape, i. e. after the head has been upset on the pin. Thus, in order to obtain a dental pin the core metal of which is covered by a pro-.- tective layer of noble metal on every surface, the

pin is coated with two or more layers of noble I metal. This process is complicated and expensive, since two or more coatings exist on the greatest part of the surface of the pin, where a single coat would be suflicient.

It has already been attempted to cap over the over the remaining shell'of noble metal. Moreover attempts have been made to cover the cut by soldering with a noble metal solder, or, when upsetting the head, to press the end of the com-' cut surface by dissolving out the base core metal L with acid, to a suitable depth, and then bending tained by pressing on to the cut surface of the pin out from the wire a small plate'of a corrosion-resistant metal .or corrosion-resistant alloy, and only then effecting the further deformation of the end face oif-v the pin. The union of the metal applied in the form of a small plate with the core metal may be effected before the deformation for example, by welding. It has further been found that even by simply pressing the plate on to the cut surface it is possible to achieve firm adhesion of the plate tothe end surface, and

this adhesion can bestill further improved by a diffusion. welding of the plate to-the shell of noble metal of the composite wire occurring on subsequent heating, for example by heating in an atmosphere free from oxygen.

The process of the present invention is very simple and therefore reliable. Plates of noble metal of any desired thickness can be applied'to the and surfaces of the pinfso that even in the case of veryextensive deformation of the end of the pin, the core metal remains covered. Factory production of the pins of the present invention can take place entirely satisfactorily.

Corrosion-resistant metals of the most diverse nature, particularly precious metals, such as gold, platinum, palladium or other metals of the platinum group, silver, and the like, or alloys containing such metals, may be used as material for the protective platesgdepending on requirements. The plates may-also comprise two or more alloys one above the other.

,The manufacture of the pins of the present invention advantageously takes place in a single apparatus in which the several successive operations are automatically coupled together. The pins cut from the wire are held by clamping means and continuously fed to the device for pressing on the small plate and then to the upsetting device. The smallprotective plate can, in this arrangement, be stamped by a die out of a strip of metal continuously passed through a slit in the guide sleeve'ofthe die, and,'by the same die, be simultaneously pressed against the wire end on the further forward movement of said die, while. if desired, itmay be electrically welded with the aid of the die, acting as electrode.

Examples of construction'of dental pins for artificial teeth, to be provided and already provided with'protective plates, in accordance with the invention, at the cut surfaces, without and with upset head and with upset heads at both ends, are illustrated by way of example on an enlarged scale in Figs. 1 to 11 of the accompanying drawing, while Fig. 12 diagrammatically i1- lustrates the production of such pins, including cutting oil? from a longer wire, application and welding-on of the protective plate and subsequent upsetting of heads at the ends of the wire.

Figs. 1 and 2 show a longitudinal section and plan-view, respectively, of a dental pin provided at one end with an upset head, of the type hitherto known, wherein the core a of base metal, provided with a coating of noble metal 11 is bared at c in the centre of the head.

Fig. 3 shows a longitudinal section of an anchor pin with a core a of base metal and a protective coating b consisting of a noble metal or layers of noble metals.

Fig. 4 shows a cross-sectionof the same pin, while Fig. 5 shows in plan and Fig. 5a shows in elevation a protective disc d suitable for covering the cut surfaces ofthis pin.

Fig. 6 shows a longitudinal section of the same pin after the protective disc (I has been mounted on one end.

Figs. 7 and 8 show a longitudinal section and plan view respectively of a pin furnished with a head by upsetting, the upsetting having been effected onlyafter application of a protective disc 11 in the manner shown in Fig. 6.

Fig. 9 shows a pin of the same type, in which the protective disc d has been homogeneously united with the coating of noble metal, for examplebefore-upsetting the head, by heating, for example by electric welding.

Fig. 10 shows such a pin having at both ends heads furnished with protective discs.

Fig. 11 shows a longitudinal section of a pin, not furnished with heads but with protective discs 11 mounted on both ends, after the welding.

-In Fig. 12, h and h denote tools, which'in the first operation, indicated at I in Fig-12, grip between themselves the wire f. guided from below upwards by a sleeve g under the action of the rolls e, after it has passed out of said sleeve 9 and thereupon cut off the portion 1' of the wire projecting above the sleeve g by sliding from right to left (viewed in the plane of the draw ing) In the second operation, shown at 2, the piece of wire 2' gripped between the ends of said tools h and h, if it is to be provided with protective discs at both ends, is displaced, by means of the die is operated by the lever 70', so far in position between the clamping members h and h that it projects approximately equal distances on both sides of said members.

In the third operation, shown at 3, the protective discs d are applied at both ends of the piece of wire clamped between the ends of the tools h and .h', by means of -a die I guided in the sleeve m and of the same diameter as the discs d, in the following manner. V

n is a slit in the sleeve m, through which is constantly passed a band (not shown in the drawing) of the material used to make the discs. After the pin i has been brought, by sliding the tools h and 71., above the-mouth of the guide sleeve m which is flared outwardly in funnel form, a small disc d, corresponding with the crossshown) the other terminal of which is connected I to frame. Suitable wiring ensures that the cir cuitis closed for a moment after the small'disc has been pressed on to the pin, the current heat occurring eflecting the welding. L

In the drawing are shown the parts needed, in this process, for stamping out the protective discs, for pressing them on to and welding them to the ends of the pin, for both ends of the pin. However in cases where a protective disc is to be provided only at one end of the pin, such devices may naturally beused only at one end. In

such cases the second operation hereinbefore referred to and illustrated in Fig, 12 is also generally dispensed with.

In the fourth operation, indicated at 4 in Fig. 12, heads are upset on the pin 1, which has now been guided still further to the left between the tools h and h, bymeans of the dies q, under the action of the levers q. In this operation also, upsetting devices of the-type illustrated in the drawing may, if desired, act only at one side, on one end of the pin 1'.

I claim: L

1. Process for the manufacture of dental pins and the like from a uniform wire consisting of a core of base metal and a coating of corrosion resistant metal cut into pieces of predetermined length having said base metal core exposed at the ends thereof which comprises pressing into cohesive contact with the exposed core and coating of a cut end of said piece a plate of corrosion-resistant metal substantially co-extensive with said cut end to form a. capped end portion having a continuous corrosion-resistant metal coating, and thereafter upsetting said capped end portion of the piece while maintaining the continuity of said coating to form an expanded anchor portion having a base metal core and a continuous corrosioneresistant coating.

2. Process for the manufacture of dental pins and the like from a uniform wire consisting of a core of base metal and a coating of corrosionresistant metal cut into pieces of predetermined length having said base metal core exposed at having a continuous corrosion-resistant metal coating, heating said end portion to eifect weldsectional shape of the wire, e. g. circular, is

stamped out of the metalband and guided on to the pin 1' bythe forward movement of the die 2, which at first is held back under the action of the pressure of the spring 0 on the other ing between said plate and said exposed core and coating, and thereafter upsetting said capped end portion of the piece while maintaining the continuity of said coating to form an expanded anchor portion having a base metal core and a continuous corrosion-resistant coating.

3. Process for the manufacture of dental pins and the like from a uniform wire consistingof a core of base metal and a coating of precious metal cut into pieces of predetermined length having said base metal core exposed at the ends thereof whichcomprises pressing into cohesive contact with the exposed core and coating of a cut end of said piece a plate of precious metal substantially co-extensive with said cut end to form a capped end portion having a continuous precious metal coating, and thereafter upsetting said capped end portion of the piece while maintaining the continuity of said coating to form an expanded anchor portion having a base metal core and a continuous corrosion-resistant precious metal coating.

4. Process for the manufacture of dental pins and the like from a uniform wire consisting of a core of base metal and a coating of precious metal cut into pieces of predetermined length having said base metal core exposed at the ends 

